(1) Field to which the invention relates
The invention relates to a method for monitoring the position of patients and/or radiation units in which a first position is taken by a camera and stored and comparison between the stored position and the second position taken by the camera takes place.
(2) The prior art
An account of such a method and an apparatus for it is given for example in the German specification (Offenlegungsschrift) No. 2,335,923. In this case scales are placed in and around the head zone of a patient for making radiological pictures. With the help of these scales and a comparison photograph position monitoring is then possible on taking in a second position.
This makes it clear that in medicine there is a great need for making it possible for the body or part of the body of a patient to be put as accurately as possible into a position which is the same as the original position, for new treatment. The more danger there is with the radiation used on the patient, the more important it is for the earlier and the later position to be the same to the greatest possible degree. So for example using radiation on a tumor it is most important that only the tumor itself and not the healthy tissue near it is put under the effect of the radiation.
So the German specification (Offenlegungsschrift) No. 2,158,457 gives an account of a positioning system for patients having the purpose of putting the patient in the same position a number of times. On the support face of the positioning system, on which the pelvis and top leg parts of the patient are to be supported, pressure and force measuring parts are placed, whose readings are used for positioning the patient at any time in the same way, that is to say in the same position. It will however be readily seen that more particularly in the case of patients, that is to say persons having a disease, great changes in weight are likely. So at the small number of points, at which the pressure and force measuring parts are used, incomplete accuracy is likely. So for example in the German specification (Offenlegungsschrift) No. 2,420,402 there is a suggestion for positioning the patient by using plastics supports, which have in them a substance, whose foaming and rapid hardening is caused. This method as well has the shortcoming that even a small loss of weight of a patient makes a space between the fitting form of the plastics support and the patient himself so that once again it is not possible to make certain that the patient will have the same position as earlier. Furthermore in addition to the complex, highly-priced and time-taking construction of a half body-shell, a great amount of space is needed, in which the body-shells are kept, from which it is possible to take them as quickly as possible for use.
Furthermore the German specification (Offenlegungsschrift) No. 2,361,155 has a system and a method for fixing and keeping a position-relation between two structures. In this respect a patient is to be put in a certain position in relation to a radiation unit and to be kept exactly in the position taken. For this purpose there is the suggestion of using a light unit with the radiation unit for producing a light ray of concentrically patterned light with an intensity changing from the middle point to the outside parts. Furthermore there is a reflecting target on the patient for reflecting the light ray of concentrically patterned light. There is also a light feeler, which is acted upon by the light reflected at the target and is so placed that a signal is produced, which is proportional to this light intensity. Furthermore a control part is used for making out the position-relation between the first and the second structure, that is to say the radiation unit and the patient. This control part is for controlling the movement of the support face for the patient. With this method and this apparatus it is for this reason only possible for the support surface, to be positioned dependent on the motion of the patient in treatment, to be in line with each movement of the patient. The outcome is that there is no undesired action of radiation at any time and wrong radiation of healthy body parts is decreased.
Furthermore however the radiation unit is to be able to be so placed that its movement is the same as that movement, used in the first treatment. This is to say that the movement of the radiation source is to be able to take place as accurately as possible along the lines of each treatment of a patient. For this purpose the German specification (Offenlegungsschrift) No. 1,766,346 has already given an account of an apparatus for the automatic adjustment of a radiation unit, in which the use of a data input makes possible regulation of the movement of the radiation unit to be the same as an earlier adjustment or movement. It is clear that such an apparatus, in addition to the most different sorts of measuring feelers and servo-motors, makes necessary a complex system for getting data and for its input and with which a movement, which has been caused to take place once, of the radiation unit can be caused to take place again.